SURFACE-PROPERTIES OF FOLDABLE SILICONE INTRAOCULAR LENSES - A STUDY USING SCANNING ELECTRON-MICROSCOPY

Background Soft intraocular lenses (IOLs) have been developed to be folded during insertion to allow implantation through a small incision. The surface of the IOL is of great importance in postoperative inflammation and long-term acceptance of the implant. Rough and sharp edges can damage delicate intraocular tissues. The purpose of this study was to analyze new, foldable silicone IOLs for surface quality prior to and following folding. Materials and methods Eleven silicone IOLs of different types were included in this study (four one-piece plate-haptic silicone IOLs and seven three-piece silicone IOLs with polypropylene, PMMA or polyimid haptics). We performed scanning electron microscopy on brand-new IOLs prior to and following folding either with forceps or inserter. Special attention was given to the silicone optic surface, optic edges, haptic-optic junctions and the haptic itself. Photographs were taken at 5-350 times magnification. Results All IOLs demonstrated a smooth and homo-geneous optic surface at low magnification. At high-power magnification (X 350), distinctive surface patterns were evident in some IOLs, which turned out to be artefacts. The edge finish showed surplus silicone material and molding flash in six of 11 IOLs. Positioning holes of the 4 plate-haptic IOLs were, except in one IOL, rounded and not rough. Photographs of the haptic-optic junctions revealed surplus material or clefts between the haptic and optic in six of the 7 three-piece IOLs; the loop ends of two IOLs showed a roughened or irregular surface. We did not detect any IOL changes produced by folding. Conclusions The silicone IOLs tested demonstrated generally acceptable surface properties, but most IOLs had regional surface irregularities of varying magnitude. The clinical impact of these remains to be established, but surplus material or surface defects might result in deposition of inflammatory cells, protein or microorganisms and synechia formation. Folding of the IOLs did not produce superficial defects.